This invention relates generally to rain rate indicators, and, more particularly, to a rain rate indicator which is capable of providing a warning indication of heavy or severe localized concentrations of rainfall.
Many storm situations produce unexpected, localized "shafts" of severe/heavy concentrations of rainfall. Measurements taken during rain storms have shown that factors of ten in rain rate variability within a matter of seconds are not uncommon. In fact, these types of measurements are consistent even in wide spread rain situations, not just in severe or heavy rain scenarios. Preliminary studies indicate that areas of heavier rainfall, up to several hundreds of meters in diameter, are imbedded within storms and that these localized "shafts" of rainfall are continuously in a state of change, thus, they will form, grow while moving with the prevailing winds, and then dissipate. Consequently, their numbers, sizes and intensities are as unpredictable as their existence is predictable.
Such heavy, localized "shafts" of severe concentrations of rainfall are of great concern, especially during the landing or takeoff of aircraft. Studies have raised the possibility that heavy rain could be a contributing factor in a number of aircraft accidents. A sufficient amount of water striking a flying aircraft can cause a significant decrease in aerodynamic lift, increase in weight, increase in drag from the force of the raindrops striking the aircraft, and the possiblity of a malfunction of the aircraft engine. Since an aircraft, especially when landing or taking off, is exceptionally vulnerable to external conditions that can alter its aerodynamic efficiency, one can easily postulate the results of such severe/heavy rainfall if a fully loaded aircraft passes through a "shaft" of severe rain at a critical point during approaching or leaving an airfield.
Consequently, aircraft safety dictates the necessity for some type of detection system to be installed at airports whereby "shafts" of severe rain can be detected over a circular area of several miles in diameter around the airport runway. Presently, the most feasible method of such rainfall rate detection is radar. Detection of rain "shafts" of relatively small diameter close to the ground, if at all possible, requires a highly sophisticated weather radar system of extremely high cost. In addition, this type of radar system must be maintained and operated by high-cost technicians. Other types of currently available rain rate indicators are ineffective since they generally react too slowly and are not designed as warning indicators of heavy rain rates.
Therefore, it is abundantly clear that some type of effective, cost efficient, and reliable severe/heavy rain warning indicator would be highly desirable. The use of this type of severe/heavy rain warning indicator although primarily applicable in conjunction with airport runways, could also find applicability in any area of use in which indication of severe or heavy rain is required.